How to reverse enum?

Question

I have an Enum class below

public class PTalkCommand {
public enum Code {
        CLR((byte) 0),
        ACK((byte) 170),
        SER((byte) 0),
        NAK         


        

Answer 1

You could add this inner class to your enum:

    public static class Backwards implements Iterable<Code> {

        @Override
        public Iterator<Code> iterator() {
            return new Iterator<Code>() {
                private Code[] codes = Code.values();
                private int i = codes.length - 1;

                @Override
                public boolean hasNext() {
                    return i >= 0;
                }

                @Override
                public Code next() {
                    if (i < 0) {
                        throw new NoSuchElementException();
                    }
                    return codes[i--];
                }

            };
        }

    }

Answer 2

There's a built-in .values() method that returns an array of all the enum constants. You can iterate it backwards.

Code[] values = Code.values();
for (int i = values.length - 1; i >= 0; i--) {
    Code next = values[i];
    //do your thing
}